%0 DATA
%A Randy
P., Sabatini
%A Brian, Lindley
%A Theresa M., McCormick
%A Theodore, Lazarides
%A William W., Brennessel
%A David W., McCamant
%A Richard, Eisenberg
%D 2016
%T Efficient Bimolecular Mechanism of Photochemical Hydrogen
Production Using Halogenated Boron-Dipyrromethene (Bodipy) Dyes and
a Bis(dimethylglyoxime) Cobalt(III) Complex
%U https://acs.figshare.com/articles/Efficient_Bimolecular_Mechanism_of_Photochemical_Hydrogen_Production_Using_Halogenated_Boron_Dipyrromethene_Bodipy_Dyes_and_a_Bis_dimethylglyoxime_Cobalt_III_Complex/2081083
%R 10.1021/acs.jpcb.5b11035.s001
%2 https://ndownloader.figshare.com/files/3713365
%K TEOA
%K quantum chemistry calculations
%K chromophore
%K hydrogen production assays
%K Photochemical Hydrogen Production
%K catalyst
%K hydrogen production
%K Efficient Bimolecular Mechanism
%K electron
%K Bodipy dyes
%K mesityl
%X A series of Boron-dipyrromethene
(Bodipy) dyes were used as photosensitizers
for photochemical hydrogen production in conjunction with [CoIII(dmgH)2pyCl] (where dmgH = dimethylglyoximate,
py = pyridine) as the catalyst and triethanolamine (TEOA) as the sacrificial
electron donor. The Bodipy dyes are fully characterized by electrochemistry,
X-ray crystallography, quantum chemistry calculations, femtosecond
transient absorption, and time-resolved fluorescence, as well as in
long-term hydrogen production assays. Consistent with other recent
reports, only systems containing halogenated chromophores were active
for hydrogen production, as the long-lived triplet state is necessary
for efficient bimolecular electron transfer. Here, it is shown that
the photostability of the system improves with Bodipy dyes containing
a mesityl group versus a phenyl group, which is attributed to increased
electron donating character of the mesityl substituent. Unlike previous
reports, the optimal ratio of chromophore to catalyst is established
and shown to be 20:1, at which point this bimolecular dye/catalyst
system performs 3–4 times better than similar chemically linked
systems. We also show that the hydrogen production drops dramatically
with excess catalyst concentration. The maximum turnover number of
∼700 (with respect to chromophore) is obtained under the following
conditions: 1.0 × 10–4 M [Co­(dmgH)2pyCl], 5.0 × 10–6 M Bodipy dye with iodine
and mesityl substituents, 1:1 v:v (10% aqueous TEOA):MeCN (adjusted
to pH 7), and irradiation by light with λ > 410 nm for 30
h.
This system, containing discrete chromophore and catalyst, is more
active than similar linked Bodipy–Co­(dmg)2 dyads
recently published, which, in conjunction with our other measurements,
suggests that the nominal dyads actually function bimolecularly.